1. Field of the Invention
The present invention relates to a vehicle headlamp capable of controlling the irradiation angle in accordance with a traveling condition of the vehicle, and to a technique for preventing glare in order to prevent a phenomenon that the irradiation direction is fixed to a not-intended direction due to an occurrence of an abnormality or a failure and so a dazzling light beam is irradiated to road users such as drivers of oncoming vehicles or walkers.
2. Related Art
An adaptive front-lighting system (AFS) capable of controlling light distribution in accordance with a travelling condition of a vehicle is arranged to, in order to perform variable light control of a light distribution, obtain steering detection information from a steering sensor and the change of the posture of the vehicle (pitch angle) calculated from a detection signal from a vehicle height sensor etc. thereby to correct the lamp unit of a headlamp in the horizontal direction and the vertical direction. Thus, it is possible to realize such an irradiation control in which the visibility in the forward and side directions of the vehicle is improved and a dazzling light beam is prevented from being irradiated to road users such as drivers of oncoming vehicles or walkers.
In such a control system, the control combined with a driving control (hereinafter referred to “swivel control) for changing the irradiation direction within the horizontal plane and a driving control (hereinafter referred to “leveling control) for changing the irradiation direction within the vertical plane is performed at suitable timings, and signals from a controller (for example, an electronic control unit such as an ECU) are sent to driving mechanisms and driving circuits for the respective operations.
For example, in a configuration in which an actuator for the swivel control and an actuator for the leveling control are mounted in a headlamp, the swivel actuator is driven in accordance with an instruction from a control device provided outside of the headlamp thereby to adjust the irradiation direction within the horizontal plane by the swivel control and further the leveling actuator is driven in accordance with an instruction from the control device thereby to adjust the irradiation direction within the vertical plane by the leveling control.
As a measure for such a case where the irradiation angle of a lamp can not be detected due to any failure, disclosed in JP-A-2002-326535 is a configuration in which the irradiation angle is restored to a preset reference angular direction thereby to prevent such a state that the irradiation direction is fixed with an abnormal angle with respect to the traveling direction of a vehicle.
When the swivel actuator becomes failure, the adjustment in the horizontal direction is made impossible or disable and so the irradiation angle is fixed in the swivel state at this time, so that a dazzling light beam may be irradiated to drivers of oncoming vehicles and circumferential vehicles. In particular, in the system including the swivel control in the light distribution control at the time of light irradiation of a low beam (or a dipped beam), since there is a difference in the height of a cut-off line between own lane (a lane on an own vehicle side) and an opposite lane, there arises a problem in a situation of being out of the suitable swivel control.
For example in the case where the left-hand traffic is defined as the road traffic law like Japan, the height of the cut-off line on the opposite lane side is directed downward by a predetermined angle (0.57°) with respect to the horizontal line thereby to prevent the occurrence of glare with respect to oncoming vehicles. In contrast, on the own lane side, a light beam is directed upward than the opposite lane side by taking the improvement of the visibility in the forward direction into consideration. Thus, if the light distribution pattern is fixed due to a failure of the actuator in a state where the light distribution pattern is directed to the opposite lane side by the swivel control, a light beam is irradiated to the opposite lane side with the light distribution which is originally arranged to irradiate preceding vehicles etc.
Thus, the running stability may be degraded depending on the circumstances.
Thus, as a measure for preventing glare at the time of occurrence of such an abnormality, disclosed in JP-A-2002-326536 is a configuration in which the irradiation direction of a lamp is changed to the downward direction thereby to prevent drives etc. of oncoming vehicles from being dazzled.
As another case, if any failure occurs at a communication line coupling the control device and the respective actuators, there arises a problem of an erroneous operation caused by unexpected swivel control or leveling control. For example, if the control signal to be originally received by the swivel actuator is not sent to the actuator, the irradiation angle is fixed at this time point.
As a countermeasure of such a phenomenon, only in the case of the communication failure, the swivel actuator restores the irradiation direction to a predetermined direction (front direction) on a condition that the swivel actuator operates normally.
The measures according to the fail safe function as explained above can be summarized in the following items.
(I) When an abnormality occurs in the swivel actuator, the lamp unit is driven by the normal leveling actuator thereby to change the irradiation direction to the downward direction.
(II) When the swivel actuator is normal but an abnormality occurs at a communication line relating to the driving control of the swivel actuator, the lamp unit is driven by the swivel actuator thereby to restore the irradiation direction to the normal direction (front direction).
As the flow of the control signal of the aforesaid case (I), a signal representing the occurrence of the swivel actuator is notified to the control device and further the control device sends the control signal to the leveling actuator thereby to correct the irradiation direction to the downward direction.
As the flow of the control signal of the aforesaid case (II), since the communication between the control device and the swivel actuator is interrupted due to the failure of the communication line, for example, it is configured to provide a self-reset function on the swivel actuator side, that is, to automatically restore the irradiation direction to the front direction when the communication failure occurs.
However, the aforesaid conventional configurations have a problem that a measure in the case that the operations responding to a failure or an abnormality etc. are performed in a duplicated manner is not considered sufficiently.
For example, in the case where the aforesaid cases (I) and (II) are simply combined, if the control device erroneously determines that an abnormality occurs on the swivel actuator side despite that an abnormality occurs at the communication system relating to the control of the swivel actuator (for example, a status signal representing that the actuator is normal is changed into a signal representing an abnormality due to the communication failure), the control device sends the control signal to the leveling actuator according to the aforesaid case (I) thereby to change the irradiation direction to the downward direction. On the other hand, the swivel actuator side determines that the communication failure occurs thereby to adjust the irradiation direction so as to be directed to the front direction according to the aforesaid case (II).
If such duplicated adjustments are performed excessively, an unsuitable irradiation state may be caused. That is, despite that the irradiation direction is restored to the front direction by driving the swivel actuator, the irradiation direction is changed further to the downward direction by the driving of the leveling actuator, whereby the visibility of own vehicle in the forward direction is degraded.
In a circumstance where an abnormality or a failure does not necessarily occur individually, it is difficult to avoid the excessive or useless control so long as a measure sufficiently considering the composite operation is not taken.